Film-Tech Forum ARCHIVE: Unstable xenon arc

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Posted by Jonathan Wood (Member # 4614) on 10-07-2016, 09:35 AM:

Hi all,

I've noticed that the 1k xenon in my Cx 20 lamphouse is making a slight electrical 'fizzing/arcing' sound. I've not noticed it before and upon examination through the observation port it seems that the arc is slightly unstable . It's not noticeable on screen and doesn't look like AC ripple. The lamp is a little long in the tooth (hence my post yesterday ) , do you wise folks think it's a sign of an aging lamp or should I be worried about the rectifier. I don't have a new lamp to try but I do have one on the way . Thanks as always , Jon

Posted by Randy Stankey (Member # 64) on 10-07-2016, 01:07 PM:

Check all the electrical connections to be sure they are secure.

What kind of power supply do you use? Is it the transformer (reactance) type and not the electronic (switcher) type? I'm going on the assumption that it's a transformer. Please correct me if I am wrong.

Start right at the incoming mains and follow through the power supply all the way to the lamp. Check your contactor, your power taps and all three (assumed) phases of your transformer.

Over time, many electrical connections can work loose due to repeated heating and cooling cycles. The connections become loose and eventually corrode.

Check, clean, tighten, repair or replace parts as necessary.

Please shut off all of the electrical breakers and lock the panel door shut before you start working on wires and things! [Wink]

I don't think that there are any major problems. It should only take you ten minutes to do this check.

If you have a reliable multimeter you should check your input and output voltages, to and from the transformer. You could check for ripple while you are at it.

Like you said, I don't think you have a problem with ripple and I don't think you have any major problems in your power supply but, for the time and effort expended, I think it is worth it even if only for peace of mind.

This should be a ten minute job that only needs a screwdriver and a meter. As I always say, try the easy things first. [Smile]

If, as you say, there is an electical arcing ("fizzling") sound coming from the projector, coming from the projector, I would bet that you simply have a loose connection, somewhere.

Afterthought: Double check that the braided cable from the xenon lamp is at least an inch or two away from anything conductive. It could be arcing to ground. It probably isn't or else the lamp might not work at all but, again, check the easy things first.

Once you've gone this far, your next suspect is the xenon lamp, itself. If it is aging, as you say, your diagnosis might be correct. Simply replacing the lamp should do the trick.

However, if you don't have a ready replacement, you might be able to nurse the existing lamp along until you get one.

Carefully remove it and inspect it.

Do I need to remind you to use protective gear? [Wink]

Be careful not to get dirt, moisture or fingerprints on the glass parts, as well. [Wink]

Look for blackened glass, deformed electrodes or other "wear and tear" problems. Replace the lamp if necessary.

If everything looks "passable" you can reinstall the lamp, making sure that all the connections are secure.

Rotating the lamp 180º (on its "roll" axis) might also help you squeeze a few more hours out of it.

Does your lamphouse have a stabilizer magnet under the lamp?
Check this, too, while you are at it. Again, this is an easy thing to check. It should only take thirty seconds.

These are all the easy things I can think of but that's the best I can do from 3,500 miles away, sight unseen. [Wink]

Posted by Jonathan Wood (Member # 4614) on 10-07-2016, 04:54 PM:

Randy, thanks so much for your detailed and well thought out reply , it's much appreciated!

I actually started doing what you suggested earlier today, although I only got as far as checking connections within the lamphouse itself, I will extend this to check back to the supply.

The Rec is a switching type (an Irem ex85g )and its running off single phase. I checked the lamp out and it looks pretty good . It's odd that it's only just started which led me to think that the rectifier could be developing a fault in its smoothing stage but since the arcing sound is coming from the lamphouse it seems likely that the fault is located somewhere within that and is , as you say, most likely just a loose connection. I will dig deeper !

Thanks again , Jon

Posted by Randy Stankey (Member # 64) on 10-07-2016, 05:00 PM:

You're welcome! [Smile]

Yes, if it's a switcher, chances are that there is little to no ripple or other problems like that but it is still worth it to check all the connections.

You know what they say about switchers? Don't you?

They run great until you have to switch it for a new one! [Wink]

Posted by Monte L Fullmer (Member # 2797) on 10-13-2016, 02:28 PM:

Check the lead connections from switcher to the igniter box (prob a IGA10M igniter) since one polarity runs through it.